A catalyst for preparing polyethylene oxide and a preparation method thereof; a method for preparing polyethylene oxide.

Abstract

This invention relates to a catalyst and preparation method for preparing polyethylene oxide (PEO), wherein the catalyst comprises a Lewis base, a Lewis acid, and a rare earth component; wherein the Lewis base is selected from bicyclic compounds containing two or three nitrogen atoms on the ring, the Lewis acid is selected from trialkylaluminum, and the rare earth component is selected from inorganic salts of rare earth elements; the molar ratio of the Lewis base, the Lewis acid, and the rare earth component is 1:(0.5-4):(0.001-0.005). In this invention, the Lewis base and Lewis acid synergistically enhance the catalytic effect of the catalyst for preparing PEO, and the presence of the rare earth component further improves the synergistic catalytic effect. The ring-opening polymerization of ethylene oxide can be carried out under mild conditions, and the obtained PEO is a high molecular weight product with a viscosity-average molecular weight of 1-4 million.

Description

Technical Field

[0001] This invention relates to the field of polymer technology, specifically to a catalyst and preparation method for preparing polyethylene oxide, and a method for preparing polyethylene oxide. Background Technology

[0002] Ethylene oxide polymers are low-toxicity, low-ash, water-soluble polymers with excellent solution rheological properties and binding effects with organic solvents. As a result, they are widely used in pulp dispersants, resin modifiers, binders, coagulants, detergents, food, personal care products, sanitary materials, cosmetics, pharmaceuticals, and quasi-pharmaceuticals.

[0003] In 2010, Colorado State University first reported the application of Lewis acid-base pairs in catalytic polymerization. Due to their high activity and ease of controlling polymerization effects, Lewis acid-base pairs have been widely studied both domestically and internationally. Recent research results indicate that Lewis acid-base pairs have shown good performance in catalyzing polymerization experiments involving epoxide / cyclic anhydride copolymerization, epoxide / CO2 (COS) copolymerization, and epoxide / cyclic anhydride / carbon dioxide copolymerization. Patent CN110483753B describes a Lewis acid-base pair catalyst system composed of zinc salts and Lewis bases (DBU, MTBD, and DBN), using hydroxyl alcohols or aliphatic primary amines as initiators to controllably catalyze the ring-opening polymerization of O-carboxylic anhydride monomers, producing a polymer with a molecular weight of 20.8 kDa. In 2018, Xinghong Zhang et al. (Cheng-Jian Zhang, Han-Yi Duan, Lan-Fang Hu, Cheng-Hui Zhang, Xing-Hong Zhang, ChemSusChemVolume 11, Issue 24, 2018, pp. 4209-4213) used triethylboron and organic bases (DBU and MTBD) to form a Lewis acid-base pair catalyst system, with alkyl alcohols as initiators, which could effectively catalyze the ring-opening polymerization of propylene oxide, producing polymers with a molecular weight of 15.2 kDa. However, the polymers prepared by existing Lewis acid-base pair catalytic systems have relatively low molecular weights, and catalyst systems for preparing polymers with molecular weights of over one million kDa have not yet been reported.

[0004] Currently, the catalysts used for the synthesis of polyethylene oxide with molecular weights in the millions are mainly alkyl metal catalysts and alkaline earth metal ammonium catalysts. Alkyl metal catalyst systems mainly include alkoxyaluminum-water-acetylenone systems, alkylaluminum-water-acetylenone systems, alkylaluminum-water-zinc acetylacetone systems, and alkylaluminum-water-rare earth metal systems, but these systems have extremely stringent requirements for water quality during preparation. Alkaline earth metal ammonium catalysts are typically prepared by reacting alkaline earth metals, such as calcium, with liquid ammonia under predetermined conditions (-34°C) to generate calcium ammonium, followed by further modification and aging. However, this catalyst system requires liquid ammonia, necessitates low-temperature conditions, and carries the risk of ammonia leakage. The synthesis of polyethylene oxide using alkyl metal catalysts and alkaline earth metal ammonium catalyst systems suffers from drawbacks such as complex processes, stringent conditions, and the need for catalyst aging. Therefore, developing new, highly efficient catalyst systems is of paramount importance. Developing a catalyst that is easy to prepare and can carry out the ring-opening reaction of ethylene oxide under mild conditions to obtain polyoxyethylene with a viscosity-average molecular weight of over 1 million is a technical problem that urgently needs to be solved. Summary of the Invention

[0005] The purpose of this invention is to provide a catalyst and preparation method for preparing polyethylene oxide, and a method for preparing polyethylene oxide to carry out the ring-opening reaction of ethylene oxide under mild conditions, thereby obtaining polyethylene oxide products with a viscosity-average molecular weight of more than 1 million.

[0006] In a first aspect, the present invention relates to a catalyst for preparing polyethylene oxide, the catalyst comprising a Lewis base, a Lewis acid, and a rare earth component; wherein the Lewis base is selected from bicyclic compounds containing two or three N atoms on the ring, the Lewis acid is selected from trialkylaluminum, and the rare earth component is selected from inorganic salts of rare earth elements; the molar ratio of the Lewis base, the Lewis acid, and the rare earth component is 1:(0.5-4):(0.001-0.005).

[0007] Optionally, the trialkylaluminum is selected from one or more combinations of triethylaluminum, tripropylaluminum, triisobutylaluminum, and n-butylaluminum.

[0008] Optionally, the bicyclic compound containing two or three N atoms on the ring has the following structural formula:

[0009]

[0010] Where X is selected from N or C, R is selected from C1-C6 alkyl or H, and n is an integer from 1 to 3.

[0011] Optionally, the bicyclic compound containing two or three N atoms on the ring is selected from one or more combinations of DBU, MTBD, and DBN.

[0012] Optionally, the inorganic salt of the rare earth element is a chloride of the rare earth element, preferably a combination of one or more of lanthanum chloride, praseodymium chloride, and yttrium chloride.

[0013] In a second aspect, the present invention relates to a method for preparing the catalyst for preparing polyethylene oxide as described in the first aspect, the method comprising: mixing a Lewis base, a Lewis acid and a rare earth component.

[0014] Thirdly, the present invention relates to a method for preparing polyethylene oxide, wherein the method uses ethylene oxide as a raw material and the catalyst for preparing polyethylene oxide prepared by the method described in the second aspect as a catalyst, or uses the catalyst for preparing polyethylene oxide described in the first aspect as a catalyst.

[0015] Optionally, the preparation method includes the following steps: dispersing the Lewis base, the Lewis acid, and the rare earth component in an organic solvent, then introducing ethylene oxide, reacting at 10–50°C for 8–40 h, and separating the solid product to obtain the polyethylene oxide product.

[0016] Optionally, the viscosity-average molecular weight of the polyethylene oxide product is 1 million to 4 million.

[0017] Optionally, the organic solvent is selected from one or more combinations of n-pentane, n-hexane, n-heptane, and n-decane.

[0018] Optionally, the preparation method further includes the following steps before introducing ethylene oxide: purging with N2 3 to 5 times, stirring, and then adjusting the temperature to the initiation temperature.

[0019] Beneficial effects:

[0020] In the catalyst for preparing polyethylene oxide of this invention, Lewis bases and Lewis acids synergistically enhance each other, and the presence of rare earth components can further improve the synergistic catalytic effect of the two. Under mild conditions, the ring-opening polymerization reaction of ethylene oxide can be carried out, and the polyethylene oxide obtained is a high molecular weight product with a viscosity-average molecular weight of 1 million to 4 million. Detailed Implementation

[0021] The present application will be further described in detail below through embodiments. Through these descriptions, the features and advantages of the present application will become clearer and more apparent.

[0022] The term “exemplary” as used herein means “serving as an example, embodiment, or illustration.” Any embodiment illustrated herein as “exemplary” is not necessarily to be construed as superior to or better than other embodiments.

[0023] Furthermore, the technical features involved in the different embodiments of this application described below can be combined with each other as long as they do not conflict with each other.

[0024] In a first aspect, the present invention relates to a catalyst for preparing polyethylene oxide, the catalyst comprising a Lewis base, a Lewis acid, and a rare earth component; wherein the Lewis base is selected from bicyclic compounds containing two or three N atoms on the ring, the Lewis acid is selected from trialkylaluminum, and the rare earth component is selected from inorganic salts of rare earth elements; the molar ratio of the Lewis base, the Lewis acid, and the rare earth component is 1:(0.5-4):(0.001-0.005).

[0025] It should be noted that in the catalyst for preparing polyethylene oxide of the present invention, Lewis bases and Lewis acids synergistically enhance each other, and the presence of rare earth components can further improve the synergistic catalytic effect. At the same time, the molar ratio of Lewis base, Lewis acid and rare earth components needs to be within the above-mentioned range to achieve good catalytic effect. Under mild conditions, the ring-opening polymerization reaction of ethylene oxide can be carried out to obtain high molecular weight polyethylene oxide, which greatly reduces energy consumption. In addition, the catalyst for preparing polyethylene oxide of the present invention has low toxicity, is easy to operate, and has mild reaction conditions, providing a new route for synthesizing environmentally friendly polyethylene oxide materials.

[0026] According to one embodiment of the catalyst of the first aspect of the present invention, the trialkylaluminum is selected from one or more combinations of triethylaluminum, tripropylaluminum, triisobutylaluminum and n-butylaluminum.

[0027] It should be noted that n-butylaluminum can also represent tri-n-butylaluminum.

[0028] According to one embodiment of the catalyst of the first aspect of the present invention, the bicyclic compound containing two or three N atoms on the ring has the following structural formula:

[0029]

[0030] Where X is selected from N or C, R is selected from C1-C6 alkyl or H, and n is an integer from 1 to 3.

[0031] According to one embodiment of the catalyst of the first aspect of the present invention, the bicyclic compound containing two or three N atoms on the ring is selected from one or more combinations of DBU, MTBD and DBN.

[0032] It should be noted that in this invention, DBU represents 1,8-diazabicyclo[5.4.0.]undec-7-ene, MTBD represents 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene, and DBN represents 1,5-diazabicyclo[4.3.0]-5-nonene. The structural formulas of the three are shown below:

[0033]

[0034] According to one embodiment of the catalyst of the first aspect of the present invention, the inorganic salt of the rare earth element is a chloride of the rare earth element, preferably a combination of one or more of lanthanum chloride, praseodymium chloride and yttrium chloride.

[0035] It should be noted that, in the catalyst described in the first aspect of the present invention, by making the trialkylaluminum one or more of triethylaluminum, tripropylaluminum, triisobutylaluminum and n-butylaluminum, and by making the bicyclic compound containing two or three N atoms on the ring selected from one or more of DBU, MTBD and DBN, and by making the rare earth component selected from one or more of lanthanum chloride, praseodymium chloride and yttrium chloride, the synergistic effect between different components in the catalyst can be further enhanced, and high molecular weight polyethylene oxide can be better obtained.

[0036] In a second aspect, the present invention relates to a method for preparing the catalyst for preparing polyethylene oxide as described in the first aspect, the method comprising:

[0037] Lewis bases, Lewis acids, and rare earth components are mixed.

[0038] It should be noted that the preparation method of the catalyst for preparing polyethylene oxide of the present invention is simple, the process conditions are mild, and the operation is convenient, which can significantly reduce the manufacturing cost of the catalyst.

[0039] Thirdly, the present invention relates to a method for preparing polyethylene oxide, wherein the method uses ethylene oxide as a raw material and the catalyst for preparing polyethylene oxide prepared by the method described in the second aspect as a catalyst, or uses the catalyst for preparing polyethylene oxide described in the first aspect as a catalyst.

[0040] According to one embodiment of the preparation method described in the third aspect of the present invention, the preparation method includes the following steps:

[0041] The Lewis base, the Lewis acid, and the rare earth components are dispersed in an organic solvent, and then ethylene oxide is introduced. The mixture is reacted at 10–50°C for 8–40 h, and the solid product is separated to obtain the polyethylene oxide product.

[0042] It should be noted that in the preparation method of polyethylene oxide of the present invention, the Lewis acid-base pair synergistic catalytic effect is used to activate the ethylene oxide monomer to perform controlled ring opening to complete the polymerization reaction. The addition of rare earth components can further improve the synergistic catalytic effect of the Lewis acid-base pair catalyst, thereby enabling the preparation of polyethylene oxide products with high molecular weight under mild conditions with a high yield of 97-99%, which also provides a new strategy and approach for the preparation of polyethylene oxide.

[0043] According to one embodiment of the preparation method described in the third aspect of the present invention, the viscosity-average molecular weight of the polyethylene oxide product is 1,000,000 to 4,000,000.

[0044] It should be noted that in the preparation method of polyethylene oxide of the present invention, based on the catalyst of the present invention, polyethylene oxide with a viscosity-average molecular weight of 1 million to 4 million can be obtained under mild and simple conditions.

[0045] According to one embodiment of the preparation method of the third aspect of the present invention, the organic solvent is selected from one or more combinations of n-pentane, n-hexane, n-heptane and n-decane.

[0046] According to one embodiment of the preparation method of the third aspect of the present invention, the preparation method further includes the following steps before the introduction of ethylene oxide:

[0047] Purge with N2 3-5 times, stir, and then adjust the temperature to the initiation temperature.

[0048] It should be noted that adjusting the temperature can lower the temperature, and the initiation temperature can be around 10℃.

[0049] The present invention will be further described in detail below through examples, but these examples are not intended to limit the invention.

[0050] Unless otherwise specified, the materials and reagents used in the embodiments and comparative examples are all commercially available, such as commercially available analytical grade chemical reagents.

[0051] Example 1

[0052] 0.01 mol DBU, 0.01 mol triethylaluminum, and 0.00001 mol praseodymium chloride were added to a 2L reactor containing 800 ml of n-hexane. The reactor was purged with N2 3–5 times. The stirrer was turned on and stirred until the compounds were completely dissolved or uniformly dispersed in the n-hexane. The temperature inside the reactor was lowered to about 10°C (the initiation temperature). 440 g of ethylene oxide was slowly added, and then the polymerization temperature was gradually increased. The polymerization reaction was carried out at 10°C–50°C for 8 hours. The solvent and the obtained polymer were separated by filtration. After vacuum drying, polyethylene oxide was obtained. The yield was 97.1%, and the viscosity-average molecular weight was 1.03 million.

[0053] Example 2

[0054] 0.01 mol DBU, 0.005 mol n-butylaluminum, and 0.00003 mol praseodymium chloride were added to a 2L reactor containing 800 ml n-hexane. The reactor was purged with N2 3-5 times. The stirrer was turned on and stirred until the compounds were completely dissolved or uniformly dispersed in the n-hexane. The temperature inside the reactor was lowered to about 10°C, the initiation temperature, and 440 g ethylene oxide was slowly added. Then the polymerization temperature was gradually increased. The polymerization reaction was carried out at 10°C to 50°C for 40 h. The solvent and the obtained polymer were separated by filtration. After vacuum drying, polyethylene oxide was obtained. The yield was 97.8%, and the viscosity-average molecular weight was 1.53 million.

[0055] Example 3

[0056] 0.01 mol MTBD, 0.012 mol triisobutylaluminum, and 0.000015 mol yttrium chloride were added to a 2L reactor containing 800 ml n-pentane. The reactor was purged with N2 3–5 times. The stirrer was turned on and stirred until the MTBD was completely dissolved or uniformly dispersed in the n-pentane. The reactor temperature was lowered to about 10°C (the initiation temperature). 440 g of ethylene oxide was slowly added, and then the polymerization temperature was gradually increased. The polymerization reaction was carried out at 10°C–50°C for 24 h. The solvent and the obtained polymer were separated by filtration. After vacuum drying, polyethylene oxide was obtained. The yield was 98.4%, and the viscosity-average molecular weight was 2.61 million.

[0057] Example 4

[0058] 0.01 mol DBN, 0.02 mol triethylaluminum, and 0.000045 mol praseodymium chloride were added to a 2L reactor containing 800 ml of n-heptane. The reactor was purged with N2 3–5 times. The stirrer was turned on and stirred until the compounds were completely dissolved or uniformly dispersed in the n-heptane. The temperature inside the reactor was lowered to about 10°C, the initiation temperature, and 440 g of ethylene oxide was slowly added. The polymerization temperature was then gradually increased. The polymerization reaction was carried out at 10°C–50°C for 32 h. The solvent and the obtained polymer were separated by filtration. After vacuum drying, polyethylene oxide was obtained. The yield was 97.8%, and the viscosity-average molecular weight was 2.1 million.

[0059] Example 5

[0060] 0.01 mol MTBD, 0.007 mol tripropylaluminum, and 0.00004 mol lanthanum chloride were added to a 2L reactor containing 800 ml n-decane. The reactor was purged with N2 3–5 times. The stirrer was turned on and stirred until the compounds were completely dissolved or uniformly dispersed in the n-decane. The reactor temperature was lowered to about 10°C (the initiation temperature). 440 g of ethylene oxide was slowly added, and then the polymerization temperature was gradually increased. The polymerization reaction was carried out at 10°C–50°C for 40 h. The solvent and the obtained polymer were separated by filtration. After vacuum drying, polyethylene oxide was obtained. The yield was 97.1%, and the viscosity-average molecular weight was 1.16 million.

[0061] Example 6

[0062] 0.01 mol DBU, 0.04 mol triethylaluminum, and 0.00003 mol lanthanum chloride were added to a 2L reactor containing 800 ml of n-heptane. The reactor was purged with N2 3–5 times. The stirrer was turned on and stirred until the compounds were completely dissolved or uniformly dispersed in the n-heptane. The temperature inside the reactor was lowered to about 10°C, the initiation temperature, and 440 g of ethylene oxide was slowly added. The polymerization temperature was then gradually increased. The polymerization reaction was carried out at 10°C–50°C for 16 h. The solvent and the obtained polymer were separated by filtration. After vacuum drying, polyethylene oxide was obtained. The yield was 98%, and the viscosity-average molecular weight was 1.02 million.

[0063] Example 7

[0064] 0.01 mol DBN, 0.015 mol n-butylaluminum, and 0.00005 mol yttrium chloride were added to a 2L reactor containing 800 ml n-decane. The reactor was purged with N2 3–5 times. The stirrer was turned on and stirred until the compounds were completely dissolved or uniformly dispersed in the n-decane. The temperature inside the reactor was lowered to about 10°C, the initiation temperature, and 440 g ethylene oxide was slowly added. The polymerization temperature was then gradually increased. The polymerization reaction was carried out at 10°C–50°C for 20 h. The solvent and the obtained polymer were separated by filtration. After vacuum drying, polyethylene oxide was obtained. The yield was 98.6%, and the viscosity-average molecular weight was 2.92 million.

[0065] Example 8

[0066] 0.01 mol DBN, 0.02 mol triisobutylaluminum, and 0.000025 mol lanthanum chloride were added to a 2L reactor containing 800 ml n-hexane. The reactor was purged with N2 3–5 times. The stirrer was turned on and stirred until the compounds were completely dissolved or uniformly dispersed in the n-hexane. The temperature inside the reactor was lowered to about 10°C, the initiation temperature, and 440 g ethylene oxide was slowly added. The polymerization temperature was then gradually increased. The polymerization reaction was carried out at 10°C–50°C for 28 hours. The solvent and the obtained polymer were separated by filtration. After vacuum drying, polyethylene oxide was obtained. The yield was 99%, and the viscosity-average molecular weight was 3.95 million.

[0067] Example 9

[0068] 0.01 mol MTBD, 0.025 mol triisobutylaluminum, and 0.000025 mol lanthanum chloride were added to a 2L reactor containing 800 ml n-heptane. The reactor was purged with N2 3–5 times. The stirrer was turned on and stirred until the mixture was completely dissolved or uniformly dispersed in the n-heptane. The temperature inside the reactor was lowered to about 10°C, the initiation temperature, and 440 g ethylene oxide was slowly added. The polymerization temperature was then gradually increased. The polymerization reaction was carried out at 10°C–50°C for 24 h. The solvent and the obtained polymer were separated by filtration. After vacuum drying, polyethylene oxide was obtained. The yield was 98.8%, and the viscosity-average molecular weight was 3.6 million.

[0069] Example 10

[0070] 0.01 mol MTBD, 0.03 mol n-butylaluminum, and 0.000015 mol yttrium chloride were added to a 2L reactor containing 800 ml n-pentane. The reactor was purged with N2 3–5 times. The stirrer was turned on and stirred until the compounds were completely dissolved or uniformly dispersed in the n-pentane. The reactor temperature was lowered to about 10°C (the initiation temperature). 440 g ethylene oxide was slowly added, and then the polymerization temperature was gradually increased. The polymerization reaction was carried out at 10°C–50°C for 28 hours. The solvent and the obtained polymer were separated by filtration. After vacuum drying, polyethylene oxide was obtained. The yield was 97.6%, and the viscosity-average molecular weight was 2.6 million.

[0071] Comparative Example 1 (Lewis acid dosage exceeded range)

[0072] 0.01 mol DBN, 0.1 mol triisobutylaluminum, and 0.000025 mol lanthanum chloride were added to a 2L reactor containing 800 ml n-hexane. The reactor was purged with N2 3-5 times. The stirrer was turned on and stirred until the compounds were completely dissolved or uniformly dispersed in the n-hexane. The temperature inside the reactor was lowered to about 10°C, the initiation temperature, and 440 g ethylene oxide was slowly added. Then the polymerization temperature was gradually increased. The polymerization reaction was carried out at 10°C to 50°C for 28 hours. The solvent and the obtained polymer were separated by filtration. After vacuum drying, polyethylene oxide was obtained. The yield was 9%, and the viscosity-average molecular weight was 16,000.

[0073] Comparative Example 2 (Lewis acid dosage exceeded range)

[0074] 0.01 mol MTBD, 0.001 mol triisobutylaluminum, and 0.000025 mol lanthanum chloride were added to a 2L reactor containing 800 ml n-heptane. The reactor was purged with N2 3–5 times. The stirrer was turned on and stirred until the mixture was completely dissolved or uniformly dispersed in the n-heptane. The temperature inside the reactor was lowered to about 10°C, the initiation temperature, and 440 g ethylene oxide was slowly added. The polymerization temperature was then gradually increased. The polymerization reaction was carried out at 10°C–50°C for 24 h. The solvent and the obtained polymer were separated by filtration. After vacuum drying, polyethylene oxide was obtained. The yield was 11%, and the viscosity-average molecular weight was 28,000.

[0075] Comparative Example 3 (Third component dosage exceeded the range)

[0076] 0.01 mol DBN, 0.02 mol triethylaluminum, and 0.000008 mol praseodymium chloride were added to a 2L reactor containing 800 ml of n-heptane. The reactor was purged with N2 3–5 times. The stirrer was turned on and stirred until the compounds were completely dissolved or uniformly dispersed in the n-heptane. The temperature inside the reactor was lowered to about 10°C (the initiation temperature). 440 g of ethylene oxide was slowly added, and then the polymerization temperature was gradually increased. The polymerization reaction was carried out at 10°C–50°C for 32 h. The solvent and the obtained polymer were separated by filtration. After vacuum drying, polyethylene oxide was obtained. The yield was 19%, and the viscosity-average molecular weight was 91,000.

[0077] Comparative Example 4

[0078] The steps described in Example 1 were repeated, except that only praseodymium chloride and triethylaluminum were added as catalysts for the preparation reaction, which were directly used for the polymerization of polyethylene oxide to obtain polyethylene oxide with a yield of 6% and a viscosity-average molecular weight of 0.4 million.

[0079] Comparative Example 5

[0080] The steps described in Example 2 were repeated, except that only praseodymium chloride and DBU were added as catalysts for the preparation reaction, which were directly used for the polymerization of polyethylene oxide to obtain polyethylene oxide with a yield of 4% and a viscosity-average molecular weight of 0.2 million.

[0081] Comparative Example 6

[0082] The steps described in Example 3 were repeated, except that only MTBD and triisobutylaluminum were added as catalysts for the preparation reaction, which were directly used for the polymerization of polyethylene oxide to obtain polyethylene oxide with a yield of 17% and a viscosity-average molecular weight of 73,000.

[0083] Comparative Example 7

[0084] 0.02 mol DBU and 0.02 mol zinc chloride were added to a 2L reactor containing 800 ml n-heptane. The reactor was purged with N2 3-5 times. The stirrer was turned on and stirred until the DBU and zinc chloride were completely dissolved or uniformly dispersed in the n-heptane. The temperature inside the reactor was lowered to about 10°C, the initiation temperature, and 440 g ethylene oxide was slowly added. The polymerization temperature was then gradually increased. The polymerization reaction was carried out at 10°C to 50°C for 24 h. The solvent and the obtained polymer were separated by filtration. After vacuum drying, polyethylene oxide was obtained with a yield of 9% and a viscosity-average molecular weight of 31,000.

[0085] Comparative Example 8

[0086] 0.02 mol DBU, 0.02 mol zinc chloride, and 0.00004 mol lanthanum chloride were added to a 2L reactor containing 800 ml of n-heptane. The reactor was purged with N2 3–5 times. The stirrer was turned on and stirred until the compounds were completely dissolved or uniformly dispersed in the n-heptane. The temperature inside the reactor was lowered to about 10°C, the initiation temperature, and 440 g of ethylene oxide was slowly added. The polymerization temperature was then gradually increased. The polymerization reaction was carried out at 10°C–50°C for 24 h. The solvent and the obtained polymer were separated by filtration. After vacuum drying, polyethylene oxide was obtained with a yield of 13% and a viscosity-average molecular weight of 43,000.

[0087] Comparative Example 9

[0088] 0.02 mol DBU, 0.02 mol diethylzinc, and 0.00004 mol lanthanum chloride were added to a 2L reactor containing 800 ml of n-heptane. The reactor was purged with N2 3–5 times. The stirrer was turned on and stirred until the compounds were completely dissolved or uniformly dispersed in the n-heptane. The temperature inside the reactor was lowered to about 10°C, the initiation temperature, and 440 g of ethylene oxide was slowly added. The polymerization temperature was then gradually increased. The polymerization reaction was carried out at 10°C–50°C for 24 h. The solvent and the obtained polymer were separated by filtration. After vacuum drying, polyethylene oxide was obtained with a yield of 11% and a viscosity-average molecular weight of 27,000.

[0089] Comparative Example 10

[0090] 0.01 mol DBU and 0.02 mol triethylboron were added to a 2L reactor containing 800 ml n-heptane. The reactor was purged with N2 3-5 times. The stirrer was turned on and stirred until the DBU and triethylboron were completely dissolved or uniformly dispersed in the n-heptane. The temperature inside the reactor was lowered to about 10°C, the initiation temperature, and 440 g ethylene oxide was slowly added. The polymerization temperature was then gradually increased. The polymerization reaction was carried out at 10°C to 50°C for 24 h. The solvent and the obtained polymer were separated by filtration. After vacuum drying, polyethylene oxide was obtained with a yield of 10% and a viscosity-average molecular weight of 21,000.

[0091] Comparative Example 11

[0092] 0.01 mol MTDB and 0.02 mol triethylboron were added to a 2L reactor containing 800 ml n-heptane. The reactor was purged with N2 3-5 times. The stirrer was turned on and stirred until the mixture was completely dissolved or uniformly dispersed in the n-heptane. The temperature inside the reactor was lowered to about 10°C, the initiation temperature, and 440 g ethylene oxide was slowly added. Then the polymerization temperature was gradually increased. The polymerization reaction was carried out at 10°C to 50°C for 24 h. The solvent and the obtained polymer were separated by filtration. After vacuum drying, polyethylene oxide was obtained with a yield of 14% and a viscosity-average molecular weight of 39,000.

[0093] Comparative Example 12

[0094] 0.01 mol MTDB, 0.02 mol triethylboron, and 0.00004 mol yttrium chloride were added to a 2L reactor containing 800 ml of n-heptane. The reactor was purged with N2 3–5 times. The stirrer was turned on and stirred until the compounds were completely dissolved or uniformly dispersed in the n-heptane. The temperature inside the reactor was lowered to about 10°C, the initiation temperature, and 440 g of ethylene oxide was slowly added. The polymerization temperature was then gradually increased. The polymerization reaction was carried out at 10°C–50°C for 24 h. The solvent and the obtained polymer were separated by filtration. After vacuum drying, polyethylene oxide was obtained with a yield of 15% and a viscosity-average molecular weight of 41,000.

[0095] Test Implementation Examples

[0096] In the above embodiments, a catalyst was prepared according to the preparation method of the present invention and the catalyst was used for the synthesis of polyethylene oxide. The yield and molecular weight of the obtained polyethylene oxide product were determined.

[0097] The relative molecular mass of polyethylene oxide was determined according to GB / T1841-1980, and the intrinsic viscosity of the polyethylene oxide product was measured. The viscosity-average molecular weight Mv (viscosity-average molecular weight) of the product was calculated based on the measured intrinsic viscosity value using the following formula:

[0098] [η] = 12.5 × 10 5 ×Mv 0.78

[0099] Where: Mv—the average relative molecular weight of the product, g / mol;

[0100] [η]——The intrinsic viscosity of the product, dl / g.

[0101] The polyethylene oxide aqueous solution used in the above determination had a mass concentration of 0.1% and a measurement temperature of 30℃. The results are shown in Table 1 below.

[0102] The yield is calculated according to the following formula:

[0103] Yield = Actual output mass of solid product ÷ Theoretical output mass × 100%.

[0104] Table 1

[0105]

[0106] Note: In Table 1 above, LB represents Lewis base, LA represents Lewis acid, the third component represents rare earth component, and EO represents ethylene oxide.

[0107] As can be seen from the above examples and comparative examples, the polyethylene oxide catalyst prepared by the method of the present invention has high catalytic activity and low dosage when applied to ethylene oxide polymerization, which significantly improves the synthesis yield of the obtained polyethylene oxide product and can synthesize high molecular weight polyethylene oxide products with a molecular weight of 1 million to 4 million.

[0108] The present application has been described above with reference to preferred embodiments; however, these embodiments are merely exemplary and illustrative. Various substitutions and modifications can be made to the present application based on these embodiments, all of which fall within the protection scope of the present application.

Claims

1. A catalyst for preparing polyethylene oxide, characterized in that, The catalyst comprises a Lewis base, a Lewis acid, and a rare earth component; wherein the Lewis base is selected from bicyclic compounds containing two or three nitrogen atoms on the ring, the Lewis acid is selected from trialkylaluminum, and the rare earth component is selected from inorganic salts of rare earth elements; the molar ratio of the Lewis base, the Lewis acid, and the rare earth component is 1:(0.5~4):(0.001~0.005). The bicyclic compound containing two or three N atoms on the ring has the following structural formula: Where X is selected from N or C, R is selected from C1-C6 alkyl or H, and n is an integer from 1 to 3.

2. The catalyst according to claim 1, characterized in that, The trialkylaluminum is selected from one or more combinations of triethylaluminum, tripropylaluminum, triisobutylaluminum, and n-butylaluminum.

3. The catalyst according to claim 1, characterized in that, The bicyclic compound containing two or three N atoms on the ring is selected from one or more combinations of DBU, MTBD and DBN.

4. The catalyst according to claim 1, characterized in that, The inorganic salt of the rare earth element is a chloride of the rare earth element.

5. The catalyst according to claim 1, characterized in that, The inorganic salt of the rare earth element is selected from one or more combinations of lanthanum chloride, praseodymium chloride, and yttrium chloride.

6. The method for preparing the catalyst for preparing polyethylene oxide according to any one of claims 1 to 5, characterized in that, The preparation method includes: Lewis bases, Lewis acids, and rare earth components are mixed.

7. A method for preparing polyethylene oxide, characterized in that, The preparation method uses ethylene oxide as a raw material and the catalyst for preparing polyethylene oxide prepared by the preparation method described in claim 6 as a catalyst, or the catalyst for preparing polyethylene oxide as described in any one of claims 1 to 5 as a catalyst.

8. The preparation method according to claim 7, characterized in that, The preparation method includes the following steps: The Lewis base, the Lewis acid, and the rare earth components are dispersed in an organic solvent, and then ethylene oxide is introduced. The mixture is reacted at 10-50°C for 8-40 hours, and the solid product is separated to obtain the polyethylene oxide product.

9. The preparation method according to claim 8, characterized in that, The viscosity-average molecular weight of the polyethylene oxide product is 1 million to 4 million.

10. The preparation method according to claim 8, characterized in that, The organic solvent is selected from one or more combinations of n-pentane, n-hexane, n-heptane, and n-decane.

11. The preparation method according to claim 8, characterized in that, The preparation method further includes the following steps before introducing ethylene oxide: Purge with N2 3-5 times, stir, and then adjust the temperature to the initiation temperature.

Images